The 38-year-old Francis Jeffers pleaded guilty to sending offensive and threatening messages to his wife Lucy at Liverpool Magistrates' Court on Wednesday, a spokesman for the Crown Prosecution Service (CPS).
The CPS officer said that Jeffers sent the WhatsApp messages to his wife after their 20-year relationship broke down and he became convinced that she was having an affair with someone else.
He told his alienated or estranged wife, 38, that her life was over and she would not need many of her clothes as she would be in a coffin.
Jeffers pleaded guilty at the Liverpool Magistrate court, to sending an offensive and threatening messages to his wife and was fined £625, ordered to pay £85 costs and a £62 victim surcharge, the CPS said.
Crown prosecutor Sophie Leyland said: "Francis Jeffers has had an impressive career as a professional footballer and is a coach with Everton FC.
"But he has embarked on a course of action that has now brought him before the courts and sent his wife menacing messages that left her genuinely fearing for her life.
"His motivation for sending the messages is irrelevant - to send messages like that is a criminal offence and he has caused his wife real distress."